The present invention relates generally to forming duct assemblies for transporting pressurized fluid therethrough such as heating and cooling air and, more particularly, to an apparatus for mechanically closing one or more Pittsburgh seams associated with metal duct sections used to form duct assemblies commonly associated with forced air HVAC systems.
Rectangular or box-shaped duct assemblies are extensively used in both commercial and residential applications to transport and distribute heated or cooled air to a building, personal residence, or other structure. Duct assemblies are conventionally formed in sections and secured together to form longer spans as needed. A duct section is typically formed of sheet metal into a rectangular shape having four sides which are joined together through the use of one or more commonly employed Pittsburgh seams.
Each duct section can be formed using a plurality of different forming techniques such as bending two pieces of sheet metal of the desired length at a 90° angle and joining such sections together along opposed complimentary edges through the use of a conventional Pittsburgh seam. This application requires the use of two Pittsburgh seams. In another method and application, all four sides of a typical duct section can be formed in a single continuous process requiring the use of a single Pittsburgh seam to join the two opposite ends of the sheet metal to form the completed duct section. In this application, a single Pittsburgh seam is needed to complete the process. Still other methods and applications may require the use of more than two Pittsburgh seams depending upon the shape and configuration of the duct section. Regardless of the number of Pittsburgh seams utilized in a particular duct assembly, these seams must be properly closed as will be hereinafter explained.
Pittsburgh seams are commonly used to join the seams of metal duct sections, whether these sections are rectangular, tapered, rounded, or some other configuration. A Pittsburgh seam includes a male portion and a female portion, the male portion being associated with one edge portion of the sheet metal portion forming the duct section and the female portion being associated with a corresponding edge portion associated with another sheet metal portion forming the duct section. The male portion of the Pittsburgh seam includes a flange portion formed along the length of one edge of the sheet metal portion which is bent over at approximately a 90° angle and is insertable into a groove or cavity associated with the female portion of the Pittsburgh seam, the female portion including an overhanging edge portion which extends beyond the partially formed seam for bending to complete the closing of the seam. During assembly of a particular duct section, the male portion of the Pittsburgh seam associated with one edge portion of a duct portion is insertable into the female portion associated with another edge portion of a duct portion so as to leave an overhanging edge portion extending beyond the partially formed seam. When the various parts of the duct section are thus pre-assembled and the duct section is formed, the Pittsburgh seams, although engaged, will not be closed or locked. In order to lock or close these seams, it is necessary to bend the overhanging edge portion of the Pittsburgh seam extending beyond the partially formed seam inwardly so that it lies adjacent to and against the outer surface of the sheet metal portion incorporating the male portion of the Pittsburgh seam. When this overhanging edge portion is bent into proper position, the Pittsburgh seam will be closed and locked.
At the present time, the commonly used Pittsburgh seam is closed either manually using a hand hammer or a power tool, or it is mechanically bent using known Pittsburgh seam closer apparatus such as the apparatus disclosed in U.S. Pat. Nos. 5,189,784; 5,243,750; and 5,353,616. Manual closing of the Pittsburgh seam is time consuming, tedious, and creates a large amount of noise. The known apparatus for mechanically closing a Pittsburgh seam require a specific orientation of the seam within the closing apparatus in order to be effective and operative in closing such seam. In this regard, operators must turn and orient the duct section so as to match the direction of the machine in closing the seam. If the duct section is not properly oriented, the seam will not be closed and a reject will occur. In addition, the known Pittsburgh seam closing apparatus do not always provide sufficient strength and support to various parts of the apparatus depending upon the force required and exerted during the seam closing process when heavier gauges of sheet metal are used to form a particular duct section; and the known prior art apparatus are not easily adjustable to accommodate different lengths of duct sections to be seamed without changing supports and other parts of the apparatus. In some circumstances, the known prior art apparatus can only accommodate certain known standard sizes of duct sections. Some of the known prior art apparatus likewise bend the sheet metal against the side wall of the duct section during the seam closing process producing wrinkles or waves in the duct seam.
It is therefore desirable to provide an improved Pittsburgh seam closing apparatus which will close a Pittsburgh seam regardless of the orientation in which the duct section is placed within the apparatus, thereby improving not only the efficiency of the seam closing process but also the efficiency of the entire assembly process in forming a duct section and moving such formed duct section to the Pittsburgh seam closer apparatus. It is also desirable to improve the overall strength of the machine and particularly the seam forming roller components and to provide an improved clamping arrangement whereby successful seaming can be accomplished from extremely light gauge metal, for example 26 gauge metal, through heavy gauge metal, for example 16 gauge metal, without the need to adjust the seam forming rollers for a tighter or looser setting. Known existing machines require adjustments for this range of metal in order to close the seam adequately or to keep from damaging either the machine or the duct section. Still further, it is also desirable to provide a Pittsburgh seam closing device which is easily and quickly adaptable for accepting and closing Pittsburgh seams associated with duct sections of any length within the machine's overall capacity without changing supports or other components of the overall apparatus. This feature will allow non-standard or odd sized duct sections to be seamed efficiently. The known existing machines are typically set for production of standard lengths of duct section and they do not allow for the closing of Pittsburgh seams associated with odd sizes of duct sections, which odd sizes are necessary and exist in every installation. Instead, these odd sized duct sections are typically seamed manually by using a hammer.
Still further, it is likewise desirable to provide a Pittsburgh seam closing apparatus wherein seam closing is accomplished without producing waves or wrinkles in the duct seam.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.